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Vitamin

Vitamin K

Also known as: K1, Phylloquinone, Phytonadione, Vitamin K

A
Evidence

A fat-soluble vitamin essential for blood clotting, bone metabolism, and cardiovascular health. Phytonadione (K1) is the plant-derived form found in leafy greens and the primary supplemental form.

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Daily target & upper limit

120 mcg / day

Vitamin K has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:

Vitamin K dosage reference →

Primary uses

  • Blood clotting
  • Coagulation support
  • Blood clotting support
  • Bone health and mineralization
  • Cardiovascular health
  • Protein carboxylation

How it works

  • Essential cofactor for clotting factors II, VII, IX, X
  • Rapidly cleared from circulation
  • Converts to MK-4 in some tissues

Dosage

Typical range
90-120 mcg daily (RDA)
Timing
With fat
With food
Yes
Duration
Usually adequate from diet
Special populations
Those on warfarin need consistent intake

Forms

  • Tablet
  • Phytonadione (K1)· 70/100
  • Menaquinone (K2)· 70/100
  • Phylloquinone· 70/100

Safety

Common side effects

  • Very safe

Contraindications

  • Warfarin users (without physician guidance)
  • Other vitamin K antagonist anticoagulants

Products containing Vitamin K

Top-scoring supplements in our catalog that list Vitamin K on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.

Thorne
Vitamin D + K2 Liquid
98
Thorne
Basic Nutrients 2/Day
93
Thorne
Basic Prenatal
93
Thorne
Advanced Nutrients
92
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Known interactions

Evidence notes

Essential for coagulation

Grade A: Multiple well-designed human trials support the main claims.

Cited research for Vitamin K

Clinical studies referenced across Formulate guides that mention vitamin k. Each links to the full study page with PubMed source + the guides that cite it.

Related in Vitamin

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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider.